---
title: "Pi-hole Disk Optimization"
description: "Resolved critical disk space issue on primary Pi-hole by reducing query log retention to 7 days, pruning Docker resources, and removing old gravity backups."
type: runbook
domain: networking
tags: [pihole, disk-space, docker, optimization, maintenance]
---

# Pi-hole Disk Optimization - 2026-02-06

## Problem

Primary Pi-hole (npm-pihole at 10.10.0.16) had critical disk space issues:
- **Root filesystem**: 91% full (27GB used of 31GB)
- **Pi-hole data**: 3.6GB total
  - `pihole-FTL.db`: 2.8GB (query log database)
  - `gravity.db`: 460MB (blocklist database)
  - `gravity.db.v5.backup`: 114MB (old v5 backup)
- **Query retention**: 91 days (default)
- **Total queries stored**: 26.4 million

## Actions Taken

### 1. Removed Old Backup Database
```bash
rm /home/cal/container-data/pihole/etc-pihole/gravity.db.v5.backup
```
**Space freed**: 114MB

### 2. Cleaned Up Docker Resources
```bash
docker system prune -af --volumes
```
**Space freed**: 4.3GB
- Removed unused images (old Pi-hole versions, Jellyfin, Foundry, etc.)
- Removed stopped containers
- Removed unused networks

### 3. Reduced Query Log Retention
```bash
echo "database.maxDBdays=7.0" >> /etc/pihole/pihole-FTL.conf
docker compose restart
```
**Configuration**: Changed from 91 days to 7 days
**Future savings**: Database will automatically maintain ~7 days of logs instead of 91

## Results

| Metric | Before | After | Improvement |
|--------|--------|-------|-------------|
| Disk Usage | 91% (27GB/31GB) | 73% (22GB/31GB) | -18% |
| Free Space | 2.8GB | 8.2GB | +5.4GB |
| Total Freed | - | 4.3GB | - |

## Ongoing Maintenance

### Automatic Cleanup
Pi-hole will now automatically:
- Delete queries older than 7 days
- Maintain FTL database size around ~300-500MB (instead of 2.8GB)
- Keep the most recent week of query logs for troubleshooting

### Manual Cleanup (if needed)
```bash
# Flush Pi-hole logs
docker exec pihole pihole -f

# Check disk usage
df -h /
du -sh /home/cal/container-data/pihole/etc-pihole/*

# Clean unused Docker resources
docker system prune -af --volumes

# Check query count
docker exec pihole pihole-FTL sqlite3 /etc/pihole/pihole-FTL.db 'SELECT COUNT(*) FROM queries;'
```

### Monitoring Recommendations

**Set up disk space alerts** when usage exceeds 85%:
```bash
# Add to cron (daily check)
0 8 * * * df -h / | awk '$5+0 > 85 {print "Warning: Disk usage at " $5 " on npm-pihole"}' | mail -s "Disk Alert" admin@example.com
```

**Check Pi-hole database size monthly**:
```bash
du -h /home/cal/container-data/pihole/etc-pihole/pihole-FTL.db
```

## Configuration File

`/etc/pihole/pihole-FTL.conf`:
```conf
database.maxDBdays=7.0  # Keep queries for 7 days only
```

## Prevention Tips

1. **Regular Docker cleanup**: Run `docker system prune` monthly
2. **Monitor disk usage**: Check `df -h` weekly
3. **Review query retention**: 7 days is sufficient for most troubleshooting
4. **Consider disabling query logging** if not needed:
   ```bash
   pihole logging off
   ```
5. **Archive old logs** before major upgrades (like v5→v6)

## Space Budget Estimates

With 7-day retention:
- **Pi-hole FTL database**: ~300-500MB (vs 2.8GB before)
- **Gravity database**: ~460MB (36 blocklists)
- **Docker images**: ~2-3GB (active containers only)
- **System overhead**: ~20GB
- **Recommended free space**: 5GB+ for headroom

**Current allocation is healthy** at 73% with 8.2GB free.